Fig. 5

TBI reduces axon diameter and myelin thickness in 4-AP and vehicle conditions. Morphological analysis of intact myelinated axons in the corpus callosum of mice treated with 4-AP or vehicle on days 1–7 post-TBI or sham condition. A A main effect of TBI results in atrophic axons regardless of vehicle or 4-AP treatment. B Intact axons have thinner myelin after TBI in both vehicle and 4-AP treated mice. C–F Scatter plots display axon diameter against g-ratio (inner axonal diameter divided by total outer diameter), since appropriate myelin thickness is related to the diameter of a given axon. The slope of the linear regression was steeper for TBI versus sham mice. This indicates myelin thinning in proportion to axon diameter after TBI. This relationship was not influenced by 4-AP treatment as compared to vehicle (E, sham p = 0.1362; F, TBI p = 0.8818). A–B Two-way ANOVA for main effect of injury or drug with Holm-Sidak’s multiple comparisons test of significance for post-hoc pair effects. Bars represent mean ± SEM with an individual data point shown for each mouse. C–F Linear regression analysis. Each circle represents a measured axon (50 axons/mouse). See Fig. 1 for mouse sample numbers and Table 3 for statistical details